State A upstream is reliant on salmon fisheries to support its tourist economy. Anglers travel from far and wide, paying significant premiums to fish for salmon in the headwaters of the river X. However, downstream state B plans to build a hydropower plant which would threaten the migratory routes of the salmon, and have a devastating effect on the salmon population upstream, the supporting ecosystems, and the local economy. Such activities are considered inconsistent with the obligation to protect the ecosystems of international watercourses, and the states must work together to mitigate the impacts that the planned hydropower developments downstream will have on upstream state A, for example through the use of fish ladders.